Ayoung man comes to the clinic with an extremely pruritic rash over his knees and elbows, which has come and gone for several years. it seems to be worse in the winter and improves with some sun exposure. examination reveals scabbing and crusting with some silvery scales. the nurse also notices small "pits" in the nails. what would account for these findings?

 All the findings reveal a Psoriasis, a disease of the skin that causes itching or painful patches of thickened and reddened skin with silvery scales. It usually appears on the shoulders, knees, scalp, back, face, palms of the hands and the soles of the feet, but can also occur in other parts of the body. Some people with this condition may acquire a form of arthritis known as psoriatic arthritis.